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x86/boot: Use unsigned comparison for addresses 

The load address is compared with LOAD_PHYSICAL_ADDR using a signed
comparison currently (using jge instruction).

When loading a 64-bit kernel using the new efi32_pe_entry() point added by:

  97aa276579 ("efi/x86: Add true mixed mode entry point into .compat section")

using Qemu with -m 3072, the firmware actually loads us above 2Gb,
resulting in a very early crash.

Use the JAE instruction to perform a unsigned comparison instead, as physical
addresses should be considered unsigned.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200301230436.2246909-6-nivedita@alum.mit.edu
Link: https://lore.kernel.org/r/20200308080859.21568-14-ardb@kernel.org
This commit is contained in:
Arvind Sankar 2020-03-08 09:08:44 +01:00 committed by Ingo Molnar
parent 8acf63efa1
commit 81a34892c2
2 changed files with 3 additions and 3 deletions
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2
arch/x86/boot/compressed/head_32.S
View File

@ -105,7 +105,7 @@ SYM_FUNC_START(startup_32)
notl %eax notl %eax
andl %eax, %ebx andl %eax, %ebx
cmpl $LOAD_PHYSICAL_ADDR, %ebx cmpl $LOAD_PHYSICAL_ADDR, %ebx
jge 1f jae 1f
#endif #endif
movl $LOAD_PHYSICAL_ADDR, %ebx movl $LOAD_PHYSICAL_ADDR, %ebx
1: 1:

4
arch/x86/boot/compressed/head_64.S
View File

@ -105,7 +105,7 @@ SYM_FUNC_START(startup_32)
notl %eax notl %eax
andl %eax, %ebx andl %eax, %ebx
cmpl $LOAD_PHYSICAL_ADDR, %ebx cmpl $LOAD_PHYSICAL_ADDR, %ebx
jge 1f jae 1f
#endif #endif
movl $LOAD_PHYSICAL_ADDR, %ebx movl $LOAD_PHYSICAL_ADDR, %ebx
1: 1:
@ -305,7 +305,7 @@ SYM_CODE_START(startup_64)
notq %rax notq %rax
andq %rax, %rbp andq %rax, %rbp
cmpq $LOAD_PHYSICAL_ADDR, %rbp cmpq $LOAD_PHYSICAL_ADDR, %rbp
jge 1f jae 1f
#endif #endif
movq $LOAD_PHYSICAL_ADDR, %rbp movq $LOAD_PHYSICAL_ADDR, %rbp
1: 1: